1. Field
Embodiments described herein relate generally to a semiconductor integrated circuit, and particularly to a semiconductor integrated circuit including a monitor circuit for monitoring characteristic of a semiconductor chip.
2. Description of the Related Art
Various kinds of measuring devices are already known as a configuration for measuring performance of a semiconductor integrated circuit formed on a semiconductor substrate.
In addition, a device is also known that measures characteristic (e.g., leakage current) of transistors in a semiconductor integrated circuit, and based on the measurement result, controls a supply voltage and a substrate bias of the semiconductor integrated circuit to suppress dispersion between the transistors in the characteristic.
As a method for measuring characteristic of transistors formed on a semiconductor substrate, a method of providing a four-terminal transistor to function as a process monitor on a dicing line of a chip is sometimes used. However, according to this method, it is necessary to provide a dedicated measuring device outside the chip. The dedicated measuring device is configured to connect to a transistor on the dicing line to measure performance of the transistors. Moreover, this method has a problem that it is difficult to specify the position of the transistor after the chip is diced.
Hence, as a method for measuring performance of transistors, there is used a method of providing a monitor circuit configured as a ring oscillator or a delay chain on the chip together with a semiconductor integrated circuit.
However, a measuring device that measures characteristic of transistors by using a ring oscillator is influenced by the rise time and fall time of both NMOS transistors and PMOS transistors. Therefore, this device cannot detect characteristic of NMOS transistors and PMOS transistors separately.